Hanna-Barbera Scooby-Doo...Mystery Comics #23

Professor Milton has invented a device that can be used to contact ghosts. Milton, Mr. Freedman (a reporter) and the gang hold hands around the device and Napoleon Bonaparte materializes. Disoriented, Napoleon knocks Milton's invention to the floor, destroying it. To prove his identity Napoleon suggests comparing his signature to an authentic autograph from the 19th century belonging to Hamilton Warner. The signatures are exactly alike, but Fred still has his doubts and seeks to discover the truth.